The present invention relates to a defined alkylpolyglucoside, to mixtures of this alkylpolyglucoside with other alkylpolyglucosides, and to the use of these alkylpolyglucosides as a cleaner concentrate.
Cleaning in place procedure is usually carried out using highly concentrated industrial alkaline hydroxide solutions, for example, 50% strength by weight sodium hydroxide solution or 45% strength by weight potassium hydroxide solution. In the corresponding works, for example, a brewery or dairy, this cleaner concentrate is diluted to customary use concentrations for the appropriate application. To increase the cleaning performance, further surfactants are customarily used.
From WO 99/21948, it is known that alkylpolyglucosides with hexyl substitution are stable in concentrated alkali metal hydroxide solutions. Thus, in the table on Page 8 of WO""948, an n-hexylglucoside is described which gave a clear solution even in 40% strength by weight sodium hydroxide solution at a concentration of 7.5%. Data on the degree of oligomerization (DP) are not contained in this publication.
The product described in United States Statutory Invention Registration H171 is likewise unsuitable for combination with highly concentrated alkali metal hydroxide solutions.
DE-A-196 07 753 describes alkylpolyglucosides with a high degree of oligomerization as high-performance surfactants for liquid detergents and cleaners. It is described in the ""753 publication how suitable alkylpolyglucosides are accessible by processing fatty alcohols and glucose in a molar ratio of 3:1 to 10:1 at temperatures in the range from 90xc2x0 to 120xc2x0 C. in an acid-catalyzed acetalation with continuous removal of the water of reaction by distillation to give alkyloligoglucosides with a low degree of oligomerization ( less than 1.6), and, following termination of the reaction, neutralizing the acidic catalyst to 0 to 90 mol %.
Following removal of such an amount of unreacted fatty alcohol, which regulates the molar ratio of the remaining fatty alcohol and glucose, based on the starting amount, to 1:1 to 3:1, the reaction mixture is subjected to post-polymerization at temperatures in the range from 90xc2x0 to 120xc2x0 C.
Following neutralization of the remaining amount of the acidic catalyst and removal of the unreacted fatty alcohol, alkyloligoglucosides are obtained which have a degree of oligomerization in the range from 1.6 to 2.5, in particular 1.6 to 2, without the products being burdened by too high a polyglucose content or inadequate color quality. In the ""753 publication, it was possible to reduce the polyglucose fraction to below 5%.
Typical examples of fatty alcohols which may be used as starting material in the process are caproic alcohol, caprylic alcohol, 2-ethylhexyl alcohol, capric alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol and behenyl alcohol, and mixtures thereof, which are produced, for example, during high-pressure hydrogenation of technical-grade methyl esters based on fats and oils or aldehydes from the Roelen oxo synthesis, and as monomer fraction during the dimerization of unsaturated fatty alcohols.
Particularly preferred technical-grade fatty alcohols are those having 8 to 10, or 12 to 18 carbon atoms, in particular hydrogenated forerun, coconut, palm, palm kernel or tallow fatty alcohol.
The acidic catalysts used are, in particular, sulfuric acid, alkylsulfuric monoesters, alkyklbenzenesulfonic acid, such as, for example, p-toluenesulfonic acid or dodecylbenzenesulfonic acid and sulfosuccinic acid. The amounts used are usually in the range from 0.1 to 5% by weight, preferably 0.5 to 2% by weight, based on the substances used.
However, the surfactants specifically disclosed in the ""753 publication are not suitable for highly concentrated alkaline cleaner concentrates.
Accordingly, there is a need to provide a highly stable polyalkylglucoside which is stable in commercially available concentrated technical-grade alkali metal hydroxide solutions and at the same time has good emulsifying power.
The above object is achieved according to the present invention by providing an alkylpolyglucoside having a degree of oligomerization (DP) of at least 1.7 to 3, where the alkyl radical comprises 8 carbon atoms. Thus, according to the present invention, ethylhexylglucoside with a degree of oligomerization in the range from 1.7 to 3 is described.
Surprisingly, it has been found that the alkylpolyglucoside of the present invention has long-term stability even in highly concentrated alkali metal hydroxide solutions based on sodium hydroxide solution or potassium hydroxide solution and does not lead to precipitations. The emulsifying power is also good in dilute alkaline cleaner solutions.
The alkylpolyglucoside according to the present invention is obtainable by a process described in detail in DE-A- 196 07 753. In this respect, the entire contents of the ""753 publication are incorporated herein by reference.
In a preferred embodiment of the present invention, the alkylpolyglucoside according to the present invention has a degree of oligomerization (DP) of from 1.85 to 2.5.
In the prior art, it is known to use cleaner concentrates based on alkylpolyglucosides having alkyl radicals in which the number of carbon atoms in the alkyl radical is other than 8 (see, for example, DE-A-196 07 753). Thus, the prior art discloses alkylpolyglucosides having an alkyl radical which comprises, in particular, 6 to 24 carbon atoms. These alkylpolyglucosides known per se can be used for the purposes of the present invention in combination with ethylhexylglucoside. For the purposes of the present invention, particular preference is therefore given to mixtures of alkylpolyglucosides of different origin than the ethylhexylglucoside, the weight ratio of the ethylhexylglucoside to the other alkylpolyglucosides being adjusted such that at least 50% by weight of the alkylpolyglucoside consist of ethylhexylglucoside.
To use the alkylpolyglucoside according to the present invention and mixtures of the inventive alkylpolyglucoside with other alkylpolyglucosides, the inventive alkylpolyglucosides are admixed with concentrated technical-grade alkali metal hydroxide solution. Commercially available technical-grade concentrated alkali metal hydroxide solutions include, for example, 50% by weight of NaOH or 45% by weight of KOH in water.
For the purposes of the present invention, particular preference is therefore given to mixtures of one or more of said alkylpolyglucosides with technical-grade concentrated alkali metal hydroxide solutions, said mixtures comprising 50 to 99.9% by weight of concentrated alkali metal hydroxide solutions and 0.1 to 50% by weight of the alkylpolyglucosides. For the purposes of the present invention, particular preference is given to corresponding mixtures which comprise 90 to 99.9% by weight of technical-grade concentrated alkali metal hydroxide solutions and 0.1 to 10% by weight of the alkylpolyglucosides.
For the purposes of the present invention, particular preference is given to the above-mentioned cleaner concentrate for the cleaning of surfaces in breweries and dairies.
The alkylpolyglucoside according to the invention is considerably less foaming, although the surface activity is not adversely affected.
The following examples are given to illustrate the present invention as well as show some advantages that are obtained therefrom.
Working Examples: